1. The Technical Field
The present invention relates generally to displays used in man/machine interfaces. More particularly, the present invention relates to displays integration of such displays into equipment panels and other substrates, displays having thin cross sections, and displays having multi-colored output.
2. The Prior Art
Displays are used to visually communicate information to users of machines as diverse as coffee makers and industrial presses. Such displays can be embodied in many forms. For example, a simple display might take the form of one or more lights that illuminate selectively to indicate the status of a machine (e.g., energized, running, stopped). A more complex display might include one or more multi-segment or dot matrix elements for providing alphanumeric information (e.g., temperature, pressure, time). A conventional display typically is provided as a pre-manufactured component or sub-assembly for later mounting to a carrier or substrate, for example, a printed wiring board or other component or panel of a machine. Such substrate or carrier may include other include other electrical/electronic components, for example, proximity sensors.
Conventional displays have numerous shortcomings. For example, they can be complicated and expensive to build. Indeed, some applications might even require custom-made displays. This can make them unsuitable for low-cost applications.
Also, conventional displays often are too thick for integration into applications requiring a low profile. Conventional displays typically comprise a substrate having a viewable surface and a rear surface. The substrate typically defines an aperture or other form of light guide for each element or segment of the display. A light source typically is surface-mounted to the rear surface of the substrate such that the light source is aligned with the aperture. When the light source is energized, light is transmitted through the aperture, which then appears as an illuminated area on the viewable surface of the substrate. In a well-designed display, each such illuminated area should be illuminated evenly. Otherwise, the display will be unattractive and difficult to read.
In order to ensure even illumination at the viewable surface, the viewable surface typically is separated from the light source by a distance sufficient to allow light emanating from the light source to fully diffuse before it reaches the viewable surface. The amount of separation required in a particular application is a function of the illuminable surface area of the display segment (e.g., aperture) and the type of light source employed, among other factors, as would be recognized by one skilled in the art. For example, the required separation generally increases as a function of illuminable surface area. Also, use of a point source, for example, a light emitting diode (LED), as the light source generally dictates greater separation than use of a light source that generates relatively diffuse light. In embodiments wherein the light source is aligned with the aperture, the required separation typically is achieved by using a substrate of a certain minimum thickness and/or by locating the light source rearward of the rear surface of the substrate. It should be apparent that this approach dictates a certain minimum overall display thickness, particularly when the display is to be post-attached to another substrate, for example, an equipment panel.
Further, the output color of a conventional display typically is determined by the color of the light source used. As such, the output color of a conventional display typically is determined at the time of manufacture and is not readily user-configurable.